The present invention is related generally to medical devices. More specifically, the present invention includes tubular sheaths for delivering intravascular blood filtering devices.
Blood vessels can become occluded in several ways. In one situation, a stenosis may be formed of an atheroma which can include a calcified material formed on the lumen walls of the blood vessel. In another situation, a stenosis can be formed of a thrombosis material which is typically softer than the calcified material, but can cause sudden and unpredictable blood flow reduction in a blood vessel lumen.
Different procedures have been developed to treat a stenotic lesion or stenosis in the vasculature. One method includes deforming the stenosis to reduce the restriction within the lumen of the blood vessel. This type of deformation is typically performed using balloon angioplasty. Another method includes the attempted removal of the stenosis or part of the stenosis. Removal of the stenotic lesion can be attempted through use of atherectomy, which can include mechanical ablation, radio frequency energy removal, and laser removal. In these methods, the stenosis can be mechanically cut or ablated from the vessel.
Problems may be encountered by the treating physician during thrombectomy and atherectomy. Stenotic debris, which may be separated from the stenosis, may be freed within the lumen of the vessel. If the debris flows distally, it can occlude distal vasculature and cause problems. If it flows proximally, it can enter the circulatory system which is also undesirable.
One technique for dealing with such debris includes filtering or otherwise removing the debris from within the vessel using an intravascular capture device. In one such method, a filtering device may be disposed distal of the stenosis during an atherectomy to catch the emboli or pieces of stenosis as they are released. These pieces or emboli may be removed using the capture device when the atherectomy procedure is complete. One such capture device includes a distal expandable filter member which can be placed distal of the stenosis to capture stenosis fragments. Expandable devices may be delivered through a delivery sheath and/or guide catheter to the treatment site. The delivery sheath and/or guide catheter may be retracted proximally prior to deploying the filter. After use, the filter may be retracted into the delivery sheath or guide catheter for removal.
What would be desirable are improved delivery sheaths for delivering distal protection devices to the treatment site. In particular, more benign delivery sheaths with distal ends that are easier to steer would be desirable.
The present invention includes delivery sheaths for intravascular emboli capturing filters, the sheath including an elongate tube having a distal region wall that is distally decreasing in thickness. In one embodiment, the distally decreasing wall thickness is imparted at least in part by a distally decreasing outside sheath diameter. In some embodiments, a tapered distal region forms a region of increasing softness relative to the more proximal adjacent region. One example of an expandable emboli filter is provided by U.S. Pat. No. 5,827,324, herein incorporated by reference.
The present invention includes intravascular emboli filtering systems including an elongate shaft having an expandable emboli filter operably coupled to the shaft distal region. The system can further include an elongate sheath having a lumen therethrough for slidably accepting the expandable emboli filter in a collapsed state. The elongate sheath preferably has a tapered, distal region having a distally decreasing wall thickness. In one embodiment, the distally decreasing wall thickness is accomplished with a distally decreasing outside diameter. One embodiment includes a substantially sudden decrease in wall thickness at the distal region, rather than a gradual taper.
In use, the emboli filter may be collapsed, and disposed within the delivery sheath distal region. A guidewire may be advanced into the patient""s vasculature and advanced further until the guidewire distal end is near the treatment site. In one method, the shaft of the emboli filter device serves as the guidewire. In another embodiment, a guidewire is first inserted, followed by the advancement of an emboli filter hollow shaft over the guidewire to a position distal of the treatment site. The emboli filter, in the collapsed state, within the delivery sheath, can be advanced together with the delivery sheath to a position near, and preferably distal of, the treatment site. The emboli filter may be advance distally out of the delivery sheath. In one method, the emboli filter is advanced distally, while the delivery sheath is held in substantially constant position. In another method, the emboli filter is held in substantially constant position, while the delivery sheath is proximally retracted.
The emboli filter, in an expanded configuration, may be left in place for the treatment process. The emboli filter may be used in conjunction with atherectomy or angioplasty procedures. After a procedure, the emboli filter may be collapsed, followed by retracting the emboli filter into the delivery sheath distal region. The emboli filter and delivery sheath may be retracted together and removed proximally from the patient""s vasculature.